The present invention relates to equipment at an elevator car for temporarily coupling a car door leaf with a shaft door leaf and for actuating a car door unlocking means. The present invention concerns the problem of allowing the opening movement of the elevator car door leaf only when the elevator car is disposed at the level of a floor, i.e. when the car door stands opposite a shaft door of the elevator.
A door drive device with a coupling mechanism for coupling a card door leaf with an associated shaft door leaf is shown in European Patent Specification EP 0 332 841. The coupling mechanism comprises two entraining runners which are oriented to be parallel to the travel direction of the elevator car and which are adjustable in their mutual spacing by a parallelogram guide with two adjusting elements each pivotable about a respective pivot axis. If the elevator car is correctly disposed at a floor level, the two entraining runners lie between two coupling elements arranged adjacent to one another at the shaft door leaf and can be laterally guided up to these (spread) in order on the one hand to unlock the shaft door leaf and on the other hand to transmit the opening and closing movement of the car door to the car door leaf in a play-free manner and synchronously. The adjustment of spacing between the two entraining runners in that case takes place by a door drive unit, which is fastened to the car door frame, by way of a linearly acting drive means (for example, by a belt drive), which also produces the closing and opening movements of the car door leaf. In that case the drive means so engages at the car door leaf by way of a pivot lever connected with the adjusting elements of the parallelogram guide that through the opening movement of the linearly acting drive means the adjusting elements are pivoted, before the start of a door leaf opening movement, into a setting in which the entraining runners are led up to the coupling elements, thereby unlock the shaft door leaf and form the coupling between the car door leaf and the corresponding shaft door leaf.
At the end of a door leaf closing movement the adjusting elements are pivoted by the closing movement of the linearly acting drive means back into a setting in which the entraining runners are spaced from the coupling elements so that the locking of the shaft door leaf in its locked position returns.
EP 0 332 841 additionally discloses equipment for unlocking the lock of a car door lock, which ensures that the car door is automatically unlocked only when the elevator car is disposed at the level of a floor, i.e. when the car door stands opposite a shaft door of the elevator.
For this purpose, one of the entraining runners has a scanning runner in the region of the outwardly disposed runner surface of that entraining runner, i.e. the runner surface co-operating with the corresponding coupling element at the shaft door leaf (coupling roller). This scanning runner extends parallel to the entraining runner and is so connected therewith by means of guide springs that in the unloaded state it is spaced a few millimeters therefrom. The contact force exerted by the coupling element on the scanning runner during a coupling process (entrainer spreading) causes displacement thereof against the spring force of the guide springs in direction towards the entraining runner. The scanning runner has a cam which transmits its displacement, which is produced by the coupling element, relative to the entraining runner and thus relative to the car door leaf to a car door lock mounted at this car door leaf and unlocks the car door leaf. If a door opening command and a resulting spreading of the entraining runners of the coupling mechanism take place when the door of the elevator car does not stand opposite a shaft door, then the entraining runners as also the scanning runner do not come into contact with one of the coupling elements at the shaft door leaves. The scanning runner is therefore not displaced relative to the entraining runner and the car door lock remains in its locking setting. A sensor monitoring the setting of the car door lock additionally prevents switching-on of the door drive motor.
This door drive device has some disadvantages.
The most significant disadvantage is that two runners, namely an entraining runner and the scanning runner guided thereat, are required on one side of the coupling mechanism. This has, on the one hand, the consequence of a high material and production cost. On the other hand, technical disadvantages result therefrom, such as losses in precision and large masses to be moved.
A further disadvantage is the relatively imprecise guidance of the scanning movement of the scanning runner by the guide springs, which requires a correspondingly larger scanning path for compensation. The limited stability of the scanning runner guidance by guide springs in the case of eccentric action of force on the scanning runner has the consequence of additional inaccuracies and thus a larger necessary scanning path. This is particularly the case when the coupling element due to variable spacing between elevator car and shaft door engages only in the lateral edge region of the scanning runner. However, larger travel paths increase the bending stresses in the guide springs and thus the risk of spring breakages.
The present invention has the object of creating equipment of the afore-described kind, which does not have the stated disadvantages.